The prior art has recognized the potential of peat moss material for use as an absorbent medium in structures for absorbing body exudate, such as sanitary napkins. The peat moss material has highly desirable fluid absorption properties such as a remarkable absorption capacity and the ability of "drying" adjoining materials by continuing to pull or wick fluid away from them over a long time period such that virtually all the fluid is collected in the peat moss core. These attributes allow the material to provide highly efficient absorbent components which can be made relatively thin for better fit, comfort and discretion, while being sufficiently absorbent to prevent overflow leakage and garment staining.
The following United States Patents document the use of peat moss material for manufacturing absorbent components for disposable absorbent products:
______________________________________ U.S. Pat. No. INVENTORS DATE ISSUED ______________________________________ 4,170,515 Lalancette et al. October 9, 1979 4,215,692 Levesque August 5, 1980 4,226,237 Levesque October 7, 1980 4,305,393 Nguyen December 15, 1981 4,473,440 Ovans September 25, 1984 4,507,122 Levesque March 26, 1985 4,618,496 Brasseur October 21, 1986 4,676,871 Cadieux et al. June 30, 1987 4,992,324 Dube February 12, 1991 5,053,029 Yang October 1, 1991 ______________________________________
The subject matter of these references is incorporated herein by reference.
Peat moss material can be formed in a highly cohesive board by using any one of the methods disclosed in the above-identified prior art. In a board form, the peat moss material is convenient to handle and it can be directly processed in high speed automatic equipment for assembling disposable absorbent products.
In broad terms, the method for producing the peat moss board consists of classifying raw peat moss material in particulate form to retain only the particles which are the most absorbent. The screened fraction is sheeted on a Fourdrinier wire in the form of a slurry and de-watered by the application of vacuum. The thus formed board is dried and calendered to increase its density to the desired level.
The raw vegetable material for manufacturing a peat moss board by the above-described method is harvested from a bog and baled into blocks having approximately a length of 1,20 meters, a width of 50 centimeters and a height of 50 centimeters. The blocks are transported to the processing site where they are defiberated and mixed with dilution water to form the slurry which is screened and delivered to the Fourdrinier wire.
A block of freshly harvested peat moss material has a very high water content, in the range from about 80% to about 95%. Accordingly, the block is prone to freezing if it is exposed to sub-zero temperatures for an appreciable amount of time. In practice, this may occur when the block of peat moss material is stored outdoors during the winter season.
When a block of peat moss freezes, it must be completely thawed before it can be further processed. One possibility is to immerse the block. of peat moss in warm dilution water which gently thaws the peat moss material without damaging in any way the peat moss fibers. However, the thawing operation is time-consuming primarily due to the substantial size of the frozen block, and also because the peat moss material has excellent thermal insulation characteristics retarding the heat transfer toward the core of the block.
Attempts to accelerate the thawing operation by using very hot dilution water have not met with success because the high water temperature risks to permanently damage the peat moss fibers and adversely affect their absorbency characteristics.
A possible solution is to mechanically reduce the block of frozen peat moss material into fragments, which would greatly accelerate the thawing operation by virtue of the increased contact surface between the warm dilution water and the frozen medium. However, it is critical to avoid a wide-spread damage at the fiber level when fragmenting the peat moss block to preserve unimpaired the absorbency characteristics of the peat moss material.